1. Field of the Invention
The invention relates to amorphous alloy layers and somewhat more particularly to amorphous alloy layers containing Ta and to a method of producing such layers.
2. Prior Art
Metal and metal-containing alloys in an amorphous state exhibit properties which are of technical interest, such as, for example, a relatively high degree of magnetic permeability, a relatively high specific electrical resistance and a relatively low or even negative value of temperature coefficient for the electrical resistance (for example, see "Journal of Chem. Physics" Vol. 48, No. 6 (1968), pages 2560-2571; "Physical Rev. B" Vol. 1, No. 12 (1970), pages 4541-4546; "Physical Rev. B" Vol. 2, No. 6 (1970), pages 1631-1743; and/or "Physics Today," Vol. 28, No. 5 (1975), John J. Gilman). Numerous methods have been developed for the production of such amorphous metals and alloys which, on the one hand, are based on stabilization of the unordered state of liquid metals or alloys via quenching, and on the other hand, on condensation of metal or other element vapors onto cooled substrates.
The so-called "Splat-Cooling" technique employs the principles of quenching and this technique has been described, for example, in "Trans. Met. Soc. of AIME," Vol. 227 (1963), pages 362-365; "ACTA Met.," Vol. 15 (1967), pages 1693-1702; or U.K. Patent Specification No. 1,476,589. The thickness of amorphous metal layers attainable with this liquid quenching technique ranges from about 10 to 100 .mu.m.
In contrast, with the "vapor quenching" technique, the materials or elements which are to form an amorphous layer are atomized onto a low temperature substrate or are condensed onto such substrate from a vapor phase. The vapor quenching technique permits extremely low layer thicknesses to be achieved, say less than 1 .mu.m, and provides a very high degree of accuracy in the thickness of the deposited layer. The quenching rate is in the order of about 10.sup.6 .degree. to 10.sup.8 .degree. K./sec. Further, this technique may be used to produce multi-component alloy layers by simultaneous deposition of a plurality of select components or elements on a cooled substrate (for example, see U.S. Pat. No. 3,427,154).
The thin amorphous alloy layers, however produced, may, if they are stable at higher temperatures, be employed in thin film technology, i.e., as in thin film resistors. However, amorphous alloy layers of this type which are formed on low temperature substrates are generally transformed into a crystalline state at higher temperatures, some even at room temperatures. In order to maintain the amorphous state of such layers over greater temperature ranges, certain "stabilizers" such as for example, Bi, B, Ge, P, Si or S are incorporated into such layers during the production thereof. However, such stabilizers or additives tend to undesirably alter the technologically useful properties of amorphous alloy layers.
In heretofore known methods of producing amorphous alloy layers via high vacuum techniques, impurities present in the residual gas were incorporated in an unordered manner within the so-formed layers. Impurities incorporated in this manner tend to stabilize the amorphous state, although they change, for example, the electrical properties of such layers and strongly reduce the reproducibility of layers having precisely determined properties.